Stents, grafts, stent-grafts, vena cava filters and similar implantable medical devices, collectively referred to hereinafter as stents, are radially expandable endoprostheses which are typically intravascular implants capable of being implanted transluminally and enlarged radially after being introduced percutaneously. Stents may be implanted in a variety of body lumens or vessels such as within the vascular system, urinary tracts, bile ducts, etc. Stents may be used to reinforce body vessels and to prevent restenosis following angioplasty in the vascular system. They may be self-expanding, expanded by an internal radial force, such as when mounted on a balloon, or a combination of self-expanding and balloon expandable.
Balloon expandable stents are typically disposed about a balloon which must be positioned and inflated to expand the stent radially outward. Self-expanding stents expand into place when unconstrained, without requiring assistance from a balloon. Some stents may be characterized as hybrid stents which have some characteristics of both self-expandable and balloon expandable stents.
Typically, a stent or other endoluminal prosthesis is implanted in a vessel at the site of a stenosis or aneurysm by so-called “minimally invasive techniques” in which the stent is compressed radially inwards and is delivered by a catheter to the site where it is required. When the stent is positioned at the correct location, the stent is caused or allowed to expand to a predetermined diameter in the vessel and the catheter is withdrawn.
In the past, stents have been generally tubular but have been composed of many configurations and have been made of many materials, including metals and plastic. Ordinary metals such as stainless steel have been used as have shape memory metals such as Nitinol and the like. Stents have also been made of bio-absorbable plastic materials. Stents have been formed from wire, tube stock, etc. Stents have also been made from sheets of material which are rolled.
In order to better provide for the precise placement of the stent within a body location some stents include radiopaque materials which may be detected through the use of fluoroscopy. In this manner the position of the stent within a body vessel may be identified. Radiopaque materials are well known and have been incorporated into stents in several ways. For example, in U.S. Pat. No. 6,402,777 rivets made of radiopaque material are positioned in stent openings; in U.S. Pat. No. 5,725,572 a stent is said to include a radiopaque material affixed to undeformed components at the distal or proximal end of the stent; and in U.S. Pat. No. 5,954,743 at least partially plating a stent with radiopaque material is described.
Stents are known to have a variety of shapes sizes and structural features. For example, stents may have a variety of lengths, diameters, cell configurations, end effects, etc. Stents may be branched or segmented for use in a vessel bifurcation. Such stents may also include one or more ports or crowns where additional stent bodies may be engaged. Some examples of stents having at least some of the structural features mentioned above are described in the following references: U.S. patent application Ser. No. 10/084,766; U.S. patent application Ser. No. 10/083,707; U.S. patent application Ser. No. 10/083,711.
In some cases it is necessary or desirable to place multiple stents, so that the stents are arranged in an end to end manner within a vessel or other body space. Recent studies have shown that in some cases, such as in some applications of drug coated stents, prevention of restenosis may be improved when the ends of adjacent stents are made to overlap one another according to a predetermined alignment. Currently however, precise multiple stent alignment wherein the overlapping stents have a preferred length of stent end overlap is difficult to achieve.
All US patents and applications and all other published documents referred to anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.